1. Field of the Invention
The present invention relates to a damping device for an electromagnetically driven printing hammer, and in particular to such a hammer which is accelerated by an electromagnetically actuated pivotable armature.
2. Description of the Prior Art
Teleprinters and other printing devices of recent construction generally utilize a plurality of character-bearing type discs which are actuated by a printing hammer. A number of structures and methods for driving the printing hammers are known in the art, however, a design goal common to all is that the printing hammer, which returns to a starting position following a printing stroke, comes to a rest in the starting position in the shortest amount of time possible so that the hammer can immediately commence the next printing stroke. It is thus necessary to remove the kinetic energy from the printing hammer within the shortest possible time after a printing stroke has occurred. A device for suddenly stopping rapidly moving masses in mechanical printers is disclosed in German OS No. 17 61 651 wherein a buffer is provided against which the mass which is to be stopped strikes. The buffer is coupled by a support consisting of damping material to a stationary frame in such a manner that the buffer can pivot around the rest position of the suppport, and moreover the buffer is dimensioned such that it largely absorbs the kinetic energy of the mass. The structure required to realize a device of this type is relatively elaborate, and is therefore not practical for use with printing hammer actuating devices of the type initially described utilizing an electromagnetically controlled actuator to accelerate the printing hammer.
A further damping structure is known from German OS No. 21 19 415 corresponding to U.S. Pat. No. 3,755,700 in which a disc comprised of shock absorbing material is utilized which is seated on a threaded pin so that the range of motion of the printing element, which is in this case a printing needle, can be adjusted. Damping achieved by this structure is not sufficient at modern printing speeds in order to rapidly bring the printing element to a rest position to ready the element for a next printing stroke, and moreover, the damping ability of the material is substantially minimized at increased temperatures and is subject to significant deterioration during aging.